Griffen was selected by the Vikings in the fourth round of the 2010 NFL Draft and has 17 1/2 sacks in 59 games. He notched a career-best eight sacks in 2012, then last year added 5 1/2 sacks.

Cassel signed with the Vikings last March to be a backup for Christian Ponder, but wound up as the starter by Week 4 when Ponder was hurt. The Vikings also signed Josh Freeman last October and all three wound up starting games for the club that finished 5-10-1.

Overall, Cassel started six games, including the last four, and played a total of nine for the Vikings in 2013. He completed 60.2 percent of his passes for 1,807 yards with 11 touchdowns and nine interceptions.

The 31-year-old veteran will likely be the starter heading into training camp. He spent four seasons with New England and four years with Kansas City before joining the Vikings.

Cassel completed 57.4 percent of his passes for 9,549 yards with 59 touchdowns and 44 interceptions during his four seasons in Kansas City. His 2010 campaign included 3,116 yards with 27 touchdowns and just seven picks, helping the Chiefs to a surprising AFC West title.

The Vikings also formally announced the re-signing of linebacker Larry Dean, who agreed to a new deal on Monday. Dean, who joined the Vikings in 2011 as an undrafted free agent, set a career-high with 18 special teams tackles in 2013.